In theory at least, I believe German softskin tilts were the same color as the vehicle. So dark grey, possibly with crew applied disruptive camo, before February 1943 and for new vehicles dunkelgelb, again sometimes with disruptive camo, afterwards. Pre-1943 dark grey vehicles repainted in dunkelgelb often seem to have the tilt left as dark grey, as shown here. The canvas tended to fade faster than the paint though. Mind you, color photos from 1940 do show a variety of colors in use, not just dark grey, especially on pre-war commercial vehicles pressed into service.
With every model I learn a little more... and then the next one takes longer!